How does an engine convert fuel into a useful from of energy?

An engine converts fuel into useful energy through a process of combustion, where fuel reacts with air to produce heat. This heat creates high-pressure gases that expand and push against engine components, such as pistons or turbines. As these components move, they perform mechanical work, converting the thermal energy from combustion into kinetic energy, which can then be harnessed to power vehicles or machinery. This process is typically governed by the principles of thermodynamics, optimizing efficiency and energy output.